Some internal combustion engines utilize a compression device such as a turbocharger to increase engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side of an engine and the compressor is coupled to an intake manifold side of the engine. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure (e.g. boost, or boost pressure) in the intake manifold and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. An actuator may be operatively coupled via a linkage to a wastegate valve and driven to position the wastegate valve anywhere between a fully open position and a fully closed position (e.g., at a valve seat) to achieve the desired boost based on operating conditions. The actuator may be an electric actuator such as an electric motor, for example.
Some wastegate actuators implement a control strategy in which one or more gain factors are used—for example, in a control strategy in which proportional, integral, and/or derivative control is employed. When PID control is employed, three control gains respectively control the contribution of the proportional, integral, and derivative terms in a relation that provides an output (e.g., a wastegate actuator position) for an input (e.g., an error such as the difference between a desired and a measured wastegate actuator position).
In some scenarios, the electric motor of a wastegate actuator may be exposed to high surrounding temperatures due to proximate flow of exhaust gasses, and may exhibit high temperatures itself, for example due to the continuous reception of high electrical currents—e.g., during operating conditions in which high or maximum boost is consistently desired. During these conditions, the current supplied to the motor may be limited to maintain the motor temperature at an acceptable level and prevent motor degradation. The control gains employed by the wastegate actuator when current supply to the motor is not limited, however, may be unsuitable for times at which current supply to the motor is limited.
U.S. Pat. App. No. 2010/0170244 describes systems and methods for adjusting controller gain in response to a current system operating condition and a static decoupling gain set comprising a plurality of gain value sets. Actuator responses may then be determined based on the adjusted controller gain and at least one error term. The actuator responses may include a turbocharger swallowing capacity modifier position such as a turbocharger wastegate position. A gain set may be selected as a function of engine speed and/or torque output, for example.
The inventors herein have recognized an issue with the approach identified above. Specifically, controller gain is not adjusted in response to limitation of the current supplied to a wastegate actuator. As such, desired wastegate control cannot be provided for operating modes in which wastegate actuator current is limited and not limited, potentially leading to undesired wastegate operation during times of actuator current limiting.
One approach that at least partially addresses the above issues includes a method comprising adjusting one or more wastegate controller gains responsive to limiting current supplied to a wastegate actuator, the current limited in response to a temperature of the wastegate actuator exceeding a threshold.
In a more specific example, adjusting the one or more wastegate controller gains includes reducing the one or more wastegate controller gains relative to respective nominal gains.
In this way, desired wastegate actuator control may be provided for operating modes in which current supply to the wastegate actuator is limited and for nominal operating modes in which current supply to the wastegate actuator is not limited. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.